1. Field of the Invention
This invention relates to a medical syringe, more particularly to a safety syringe with an automatically retractable needle.
2. Description of the Related Art
After using a disposable medical syringe, the user may be injured by accidental puncture of a needle of the syringe. PCT Application No. 000287 and U.S. Pat. Nos. 5,395,337 and 6,077,245 disclose safety syringes that are provided with retractable needles, which can be withdrawn into syringe barrels or plungers by means of a negative pressure or a spring force to prevent accidental puncture. However, the structures of the aforesaid conventional safety syringes are too complex to fabricate at relatively low costs.